1. Field of the Invention
The present invention relates to a method for manufacturing an electron beam apparatus supporting member arranged in an airtight container in an electron beam apparatus having the airtight container in which an electronic source is contained, an electron beam apparatus supporting member manufactured by using the method, and an electron beam apparatus such as an image-forming apparatus having the electron beam apparatus supporting member.
2. Related Background Art
Conventionally there are known two types of electron-emitting devices; a hot-cathode device and a cold-cathode device. As the cold-cathode device among these, there are known a surface conduction electron-emitting device, a field emission device (hereinafter also referred to as an FE device), and a metal-insulator-metal emission device (hereinafter also referred to as an MIM device), for example.
The surface conduction electron-emitting device utilizes a phenomenon that electrons are emitted by flowing current on a thin film having a small area formed on a substrate, so as to be in parallel with its film surface. As the surface conduction electron-emitting device, there are known one with an SnO2 thin film [M. I. Elinson, Radio Eng. Electron Phys., 10, 1290, (1965)], one with an Au thin film [G. Dittmer: “Thin Solid Films,” 9, 317 (1972)], one with In2O3/SnO2 thin film [M. Hartwell and C. G. Fonstad: “IEEE Trans. ED Conf.,” 519 (1975)], and one with a carbon thin film [Hisashi Araki et al.: “Vacuum,” vol. 26, No. 1, 22 (1983)], for example.
As a typical example of a device configuration of these surface conduction electron-emitting devices, FIG. 15 shows a plan view of a surface conduction electron-emitting device with an In2O3/SnO2 thin film to M. Hartwell et al. as set forth in the above. In the surface conduction electron-emitting device with an In2O3/SnO2 thin film, an electroconductive thin film 904 made of metallic oxide is formed in a sputtering process on a surface of an insulating substrate 901 as shown in FIG. 15. The electroconductive thin film 904 is formed in an H-shaped plane as shown in FIG. 15. The electroconductive thin film 904 is subjected to an energization operation called energization forming described later, by which an electron-emitting region 905 is formed in a central portion of the electroconductive thin film 904. A gap L shown in FIG. 15 is set to 0.5 to 1 mm and a width W of a region where there is formed the electron-emitting region 905 of the electroconductive thin film 904 is set to 0.1 mm. While the electron-emitting region 905 is represented by a rectangle in the center of the electroconductive thin film 904 in FIG. 15, a position and a shape of the electron-emitting region 905 are typical ones and they do not represent a position and a shape of an actual electron-emitting region 905 faithfully.
Giving an example of FIG. 15 for a description in the above surface conduction electron-emitting devices including the device to M. Hartwell, generally the electroconductive thin film 904 is subjected to an energization operation called energization forming before an electron emission, by which the electron-emitting region 905 is formed on the electroconductive thin film 904,. The energization forming means that a constant dc voltage or a dc voltage increasing at a very slow rate of approx. 1 V/min or so, for example, is applied at both ends of the electroconductive thin film 904 for energizing in order to destruct, deform, or change in quality the electroconductive thin film 904 locally to form the electron-emitting region 905 having an electrically high resistance on the electroconductive thin film 904. At this point, a fissure is generated in a part of the electroconductive thin film 904 locally destructed, deformed, or changed in quality. If a voltage is appropriately applied to the electroconductive thin film 904 after the above energization forming, an electron emission occurs in the vicinity of the fissure generated in the electroconductive thin film 904.
In addition, as FE devices, there are known one described in “Field emission,” Advance in Electron Physics, 8, 89 (1956) to W. P. Dyke & W. W. Dolan et al. or one described in “Physical properties of thin-film field emission cathodes with molybdenium cones,” J. Appl. Phys., 47, 5248 (1976) to C. A. Spindt et al.
As a typical example of the FE devices, FIG. 16 shows a sectional view of a device to C. A. Spindt et al. as set forth in the above. In a conventional FE device, as shown in FIG. 16, emitter wiring 961 made of electroconductive materials is formed on a substrate 960 as shown in FIG. 16. On the surface of the emitter wiring 961, an emitter cone 962 and an insulating layer 963 are formed, respectively, and a gate electrode 964 is formed on a surface of the insulating layer 963. This FE device emits an electric field from a tip portion of the emitter cone 962 by applying a voltage appropriately to a portion between the emitter cone 962 and the gate electrode 964.
As another configuration of the FE device, there is a structure in which an emitter and a gate electrode are arranged on a substrate almost in parallel with a surface of the substrate instead of the laminated structure as shown in FIG. 16.
As an MIM device, there is known one described in C. A. Mead, “Operation of tunnel-emission Devices,” J. Appl. Phys., 32, 646 (1961), for example. Referring to FIG. 17, there is shown a sectional view showing a typical example of the MIM device. In a conventional MIN device, as shown in FIG. 17, a lower electrode 971 made of a metal is formed on the substrate 970. On a surface of the lower electrode 971, a thin insulating layer 972 having a thickness of approx. 100 angstroms is formed on a surface of the lower electrode 971 and an upper electrode 973 made of a metal having a thickness of approx. 80 to 300 angstroms on a surface of the insulating layer 972. In this type of the MIM device, a voltage is appropriately applied to a portion between the upper electrode 973 and the lower electrode 971, by which electrons are emitted from a surface of the upper electrode 973.
The above cold-cathode device is capable of achieving an electron emission at a lower temperature in comparison with the hot-cathode device, and therefore it does not need a thermal heater. Accordingly, the cold-cathode device has a configuration simpler than that of the hot-cathode device, by which it can be manufactured as a fine device. Additionally even if a lot of cold-cathode devices are arranged at a high density on the substrate, it does not easily have a problem such as heat fusion on the substrate. Furthermore, the cold-cathode device has an advantage of a rapid response contrary to the hot-cathode device whose response speed is relatively low since it is operated by heating with the heater.
Accordingly, research on applications of the cold-cathode device has been actively performed.
For example, the surface conduction electron-emitting device has a particularly simple configuration among cold-cathode devices and is easy to manufacture, thus having an advantage that a lot of devices can be formed over a large area. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 64-31332 to this applicant, for example, research has been done on a method for driving with arranging a lot of surface conduction electron-emitting devices. As for an application of an electron beam apparatus using this type of a surface conduction electron-emitting device, research has been done on image-forming apparatuses such as an image display and an image recording apparatus and charging beam sources, for example.
Particularly as an application of an electron beam apparatus to an image display, as disclosed in specifications of U.S. Pat. No. 5,066,883 to this applicant, Japanese Patent Application Laid-Open No. 2-257551, and Japanese Patent Application Laid-Open No. 4-28137, for example, research has been done on an image display using a surface conduction electron-emitting device combined with phosphor which emits light by means of irradiation of an electron beam from the surface conduction electron-emitting device. The image display using the surface conduction electron-emitting device combined with the phosphor is expected to have characteristics superior to those of other types of conventional image displays. Accordingly, the image display to which the electron beam apparatus is applied is superior in that it does not need a back light since it is of a self light emission type and in that it has a wide view angle, in comparison with liquid crystal display units which have been spreading in recent years, for example.
A method for driving with arranging a lot of FE type devices is disclosed in specifications of U.S. Pat. No. 4,904,895 to this applicant, for example. In addition, as an example of an application of an FE type device to an image display, there is known a flat panel display suggested by R. Meyer et al. [R. Meyer: “Recent Development on Micro-tips Display at LETI,” Tech. Digest of 4th Int. Vacuum Microelectronics Conf., Nagahama, pp. 6 to 9 (1991)], for example.
Furthermore, as an example of an application of a lot of arranged MIM-type devices to an image display, there is an image display disclosed in Japanese Unexamined Patent No. 3-55738 to this applicant, for example.
A flat panel display having a short depth is space-saving and light in weight among the above image-forming apparatuses to which the above electron beam apparatus having the electron-emitting device is applied, thereby drawing public attention as a display superseding a CRT display.
Referring to FIG. 18, there is shown a perspective view showing an example of a display panel portion in a conventional flat panel display to which the electron beam apparatus is applied, in which a part of the panel is illustrated in a cutaway view to show an internal structure of the display panel portion.
In the display panel portion in the conventional flat panel display, a substrate 911 is mounted on a surface of a rear plate 915 as shown in FIG. 18. A sidewall 916 is bonded to an edge portion of the surface of the rear plate 915 therealong. A face plate 917 opposite to the rear plate 915 is bonded to a surface of the sidewall 916 opposed to the rear plate 915. The face plate 917, the sidewall 916, and the rear plate 915 form an airtight container (envelope) 931 of the display panel sealed to keep an inside of the display panel in a vacuum, with the face plate 917, the sidewall 916, and the rear plate 915 each forming a wall portion of the sealed container 931.
On the substrate 911 fixed to the rear plate 915, cold-cathode devices 912 are formed in a matrix by N×M. N and M are positive integers equal to or greater than 2 and values of N and M are appropriately set according to the target number of pixels of a display. The N×M of cold-cathode devices 912 are coupled to each other with row-directional wiring 913 of M wires and column-directional wiring 914 of N wires as shown in FIG. 18. A multiple electron beam source 932 comprises the substrate 911, the cold-cathode devices 912, the row-directional wiring 913, and the column-directional wiring 914 in the above. In an at least intersecting portion of the row-directional wiring 913 and the column-directional wiring 914, an insulating layer (not shown) is formed therebetween, so that the row-directional wiring 913 is kept to be electrically insulated from the column-directional wiring 914 in the intersecting portion.
A phosphor film 918 made of phosphor is formed on a lower surface of the face plate 917 in the rear plate 915 side, and the phosphor film 918 is made of phosphor materials having three primary colors; red (R), green (G), and blue (B) (not shown). In addition, a black material (not shown) is formed between the above colored phosphor materials forming the phosphor film 918 and a metal back 919 made of Al or the like is formed on a surface of the phosphor film 918 in the rear plate 915 side. This metal back 919 is used as a control electrode for controlling electrons emitted from the cold-cathode device 912, and an accelerating voltage for affecting the electrons is applied to those so as to accelerate the electrons emitted from the cold-cathode devices 912.
On the sidewall 916, terminals Dx1 to Dxm, Dy1 to Dyn, and Hv for electrical connections in the airtight structure are mounted to connect electrically the row-directional wiring 913, the column-directional wiring 914, and the metal back 919 of the display panel to an electrical circuit which is not shown in an outside of the display panel. These terminals are protruding from the sidewall 916 to an outside of the airtight container 931. The terminals Dx1 to Dxm are electrically connected to the row-directional wiring 913 corresponding to the terminals Dx1 to Dxm, respectively, the terminals Dy1 to Dyn are electrically connected to the column-directional wiring 914 corresponding to the terminals Dx1 to Dxm, respectively, and the terminal Hv is electrically connected to the metal back 919.
The inside of the airtight container 931 is maintained in a vacuum of approx. 10−6 Torr, and therefore, as a display area of the image display becomes larger, there occurs a need for means of preventing the rear plate 915 and the face plate 917 from being deformed or destroyed due to a difference between atmospheric pressures of the inside and the outside of the airtight container 931. In using a method of increasing a thickness of the rear plate 915 and of the face plate 917 to prevent them from being deformed or destroyed, not only a weight of the image display is increased, but a distortion or a parallax error occurs when a display surface is viewed in an oblique direction. On the other hand, as shown in FIG. 18, there are provided spacers (also referred to as ribs) 920 as electron beam apparatus supporting members each made of a relatively thin glass plate for bearing an atmospheric pressure between the substrate 911 and the face plate 917. The rear plate 915 and the face plate 917 are supported by the spacers 920, by which a submillimeter to several millimeters of a gap is normally maintained between the substrate 911 composing a multiple electron beam source 932 and the face plate 917 on which the phosphor film 918 is formed and an inside of the airtight container 931 is kept in a high vacuum as described above.
When a voltage is applied to the cold-cathode devices 912 through the terminals Dx1 to Dxm and Dy1 to Dyn protruding outside the airtight container 931 in the image display having the above-described display panel, electrons are emitted from the respective cold-cathode devices 912. Simultaneously with it, a high voltage of hundreds of volts to thousands of volts is applied to the metal back 919 through the terminal Hv to accelerate electrons emitted from the cold-cathode devices 912 so that the accelerated electrons collide with an inner surface of the face plate 917. This excites phosphor materials having respective colors composing the phosphor film 918, by which they emit lights to display an image on a display screen on the display panel.
On the display panel shown in FIG. 18, a part of electrons emitted from the cold-cathode devices 912 in the vicinity of the spacers 920 collide with the spacers 920 or ions ionized due to an effect of the emitted electrons adhere to the spacers 920, by which static electrification may occur on the spacers 920. If this static electrification occurs on the spacers 920, a trajectory of the electrons emitted from the cold-cathode devices 912 is excessively curved and the electrons having the excessively curved trajectory reach positions different from normal positions on the phosphor of the phosphor film 918, by which an image in the vicinity of the spacers 920 is distorted on the display disadvantageously.
If any of the spacers 920 moves off the original position due to an assembly error of the display panel at this point, a distance between the spacer 920 and the cold-cathode device 912 partially narrows and the difference of the electron trajectory is significantly increased. In this manner, the distortion of the image on the display screen is further extended by a positional difference of the spacer 920, too.
In addition, a high voltage of hundreds of volts, in other words, 1 kV/mm or higher electric field is applied to a portion between the multiple electron beam source 932 and the face plate 917 to accelerate the electrons emitted from the cold-cathode devices 912, by which a creeping discharge may occur on a surface of the spacer 920. Particularly if the spacers 920 are charged as described above, discharging may be caused by the high voltage.
If any of the spacers 920 moves off the original position due to an assembly error of the display panel at this point, the distance between the spacer 920 and the cold-cathode device 912 partially narrows, too, which increases a probability of giving an extended damage on the cold-cathode devices 912 at discharging caused by static electrification of the spacers 920, thus accelerating a deterioration of the cold-cathode devices 912 disadvantageously.
To solve these problems, there have been suggested methods for removing static electrification of the spacers 920 by flowing microcurrent through the spacers 920 in Japanese Patent Application Laid-Open No. 57-118355 and Japanese Patent Application Laid-Open No. 61-124031. In these methods in the official gazettes, a high resistance thin film is formed as an antistatic film on a surface of an insulating spacer substrate and is formed as a spacer comprising spacer electrodes put on the upper and lower surfaces of the spacer substrate, so that microcurrent flows uniformly over the surfaces of the spacer through the spacer electrodes. As for materials of the antistatic film, a tin oxide film, a mixed crystal thin film made of tin oxide and indium oxide, or a metal film is used.
Referring to FIG. 19, there is shown a flowchart for explaining a spacer manufacturing process according to a conventional technology. In the conventional spacer manufacturing process, a substrate is made first to form a spacer substrate by molding a base material made of the same component material as for the spacer substrate having a larger shape than one for the spacer substrate composing the spacer (S11). Second, by cutting the substrate (S12), the spacer substrate is cut off from the substrate to manufacture the spacer substrate. Next, a high resistance film is formed on a surface of the spacer substrate as an antistatic film (S12), and further spacer electrodes are partially formed on the spacer substrate on which the high resistance film is formed (S14), by which a spacer is manufactured having the high resistance film and the spacer electrodes formed on the spacer substrate.
There is such a problem, however, in forming a high resistance film or spacer electrodes on an insulating spacer substrate when manufacturing a spacer which is an electron beam apparatus supporting member that the number of processes is increased or a manufacturing process is complicated, which leads to an increase of a manufacturing time or of a manufacturing cost, thereby easily deteriorating a mass production property.